An automated, low-altitude air traffic control system for drones is just one of the suggestions to come out of a European Commission-sponsored paper on re-regulating drone use.

The usual way of cleaning off moss is to send someone up in a cherry-picker, but this is costly, time-consuming and potentially dangerous. With the drone, it's just a matter of flying close to the insulator and spraying a moss remove agent onto the glass discs. Within a few days, the moss will dry up and drop off -- or so the theory goes. Engie's prototype uses standard industrial valves and actuators to orient the nozzle and turn on the spray. A pressurized steel canister holds the cleaning fluid -- which is nothing special, according to Engie research engineer Patrick Subreville: It's the same stuff he used to remove moss from the roof of his house last summer.

To comply with local laws, Engie's moss-removal test flights must take place inside a net enclosure, one pilot guiding the drone and another directing the spray.

The EU's proposed safe space for drone flights could open up commercial opportunities for this and many other applications.